How to write to a file different parameters from different CallBacks with same timestamp?

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Hello

I would like to write to a text file different parameters obtained from different topics (scan, raw_imu, odom). I obtained some parameters in different CallBacks like scanCallback poseCallback, imuCallback. I would like to have those output parameters in on file but synchronized (with same frequency, like for example every 1 second.)

I know that can use the commands

myfile.open("/home/user/file.ttx");
myfile << "timestamp" << "....  "\n";

But I cant make it that all output parameters are written in same time stamp. Like for example

time in sec    parameter1   parameter2   parameter3
1                 value      value        value
2                 value      value        value
3                 value      value        value

I know that laser scaner and Imu publish with different frequencies.

Any help?